What's the different between CharacterView and UnicodeScalarView of the String type

This comes down to the difference between a Character and UnicodeScalar.

Unicode Scalars

Behind the scenes, Swift’s native String type is built from Unicode scalar values. A Unicode scalar is a unique 21-bit number for a character or modifier, such as U+0061 for LATIN SMALL LETTER A ("a"), or U+1F425 for FRONT-FACING BABY CHICK ("

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